1. Field of the Invention
This invention relates to a noncontact type batteryless IC card which can be used as, for example, a personal identification medium of an entry and exit management device, a resident register card and the like, which performs by receiving a power wave transmitted from a card reader-writer and generating an operating voltage from the received power wave, and which allows data to be written in or read from a rewritable nonvolatile memory by making radio communications with the card reader-writer, and also relates to a system of the noncontact type IC card.
2. Description of the Related Art
Recently, for example, a noncontact type IC card called a radio card has been used as a personal identification medium of an entry and exit management device. The noncontact type IC card storing personal physical characteristic information and the like is distributed to a visitor. The card collates the physical characteristic information by making radio communications with a card reader-writer installed at a room entrance and controls opening and closing of an entrance door.
Such a noncontact type IC card called a radio card is typically in a batteryless type for the purpose of reduction of the battery exchange operation, downsizing, decrease in manufacturing costs, extension of life and the like.
Thus, a recent noncontact type IC card is operated to receive a power wave transmitted from the card reader-writer, generate an operating voltage from the received power wave and supply the operating voltage to each section.
Incidentally, in this kind of noncontact type IC card, for example, when data is stored (written) in the nonvolatile memory on the basis of a write instruction transmitted from the card reader-writer, a method of writing the supplied data that should be written in the nonvolatile memory at only one time is employed.
In the conventional method, data is written in the nonvolatile memory even if the noncontact type IC card is under any conditions. However, power supply in this kind of the noncontact type IC card may be remarkably unstable in accordance with the state of the received wave. If the one-time writing is failed, the data may not be stored.